Right-wing candidate Abelardo De La Espriella won the Colombian presidential elections in a tight race on Sunday.
De La Espriella, 47, has proposed a tough crackdown on crime, as well as the end to peace talks with armed groups and a boost to Colombia's oil and gas sector.
Iván Cepeda Castro, 63, the leftist competitor in the presidential race, vowed to continue the policies of President Gustavo Petro, a former rebel and the country's first leftist president.
These policies include state pension payments for the poor, union-backed labor reforms, peace talks with armed groups that have fought the state for decades, and a moratorium on new oil projects.
De La Espriella blames Petro for the country's economic and security woes and has vowed to lower taxes and reduce the size of the state by up to 40%, but has said he will preserve Petro's 23% increase in the minimum wage, along with other popular social measures.
400,000 voters turned in blank ballots in protest, Cepeda contests results
Whoever wins will grapple with high public debt and a divided Congress, which could stymie reform proposals.
Some 400,000 voters turned in blank ballots, usually seen as a protest vote.
Cepeda said on Sunday that he will await a final, ballot-by-ballot check of an initial presidential vote count, saying his campaign is challenging results from some 33,000 ballot boxes.
Cepeda notched 48.7% support, data from the country's national registry office showed, less than 1% behind right-wing lawyer Abelardo De La Espriella, who won 49.65%. The difference between the two men is equivalent to some 246,000 votes.
The head of the national registrar, Hernan Penagos, said separately that verification was beginning at a municipal level and would soon extend across the country. A final count, overseen by notaries and judges, is required by Colombian law.